The mass-market appeal of movie, television, and sports has created a demand for confections and other food articles with multi-colored decorations bearing the likenesses of media figures. Bakeries, supermarkets and other food retailers have used increasingly sophisticated printing techniques to create these images on food articles.
For example, in a screen printing process, positive images are created from an artwork design. Using this positive image, printing screens are exposed and developed to include a negative image of the artwork design. A first color of an edible ink is then sprayed through the screen and onto a surface of a substrate, typically an icing layer or a sugar sheet, to form an image layer on the surface of the substrate. This step is repeated, one color at a time, until the multi-colored image is formed on the surface of the substrate. In another well known process, a first color of an edible ink may be applied to a pad of an automatic pad transfer printer. The pad is then contacted with a hard, non-porous surface of an icing layer on a confection to form an image layer thereon. This step is repeated, one color at a time, until a multi-colored image layer is formed. In the alternative, the artwork may be electronically scanned and the image file downloaded to an ink jet printer having a cartridge filled with at least one edible ink. The ink jet printed then applies the ink to a surface of a substrate to form an image layer thereon.
These techniques are much more efficient than a hand decorating process, and have made possible the creation of larger numbers of high-quality decorated food articles for purchase by a consumer. However, these techniques are relatively slow and unsuited for high volume production of food articles.
In the commercial printing industry, lithographic printing processes are routinely used for high volume production of highly precise single or multi-colored images on paper articles. In the lithographic process, also referred to as offset, litho-offset, web and offset lithography, an ink receptive image is typed or drawn on a master or produced photographically on a sensitized photopolymer plate. An ink is applied to the imaged master or plate to form an ink layer thereon, and the master is then placed on the master cylinder of an offset printing press. The ink layer built up on the master is then transferred to a surface of a rubber blanket cylinder, and the ink layer is subsequently transferred to a paper substrate as the paper passes between the blanket cylinder and an impression cylinder.
Compared to screen printing or inkjet printing processes, lithographic printing makes possible increased production speeds, improved quality in the reproduction of fine tones, and a substantial reduction in the number of impressions required to reproduce full color images.